Encoder, decoder, system and methods for encoding and decoding

ABSTRACT

Embodiments of the present invention provide an encoder including a quantization stage, an entropy encoder, a residual quantization stage and a coded signal former. The quantization stage is configured to quantize an input signal using a dead zone in order to obtain a plurality of quantized values. The entropy encoder is configured to encode the plurality of quantized values using an entropy encoding scheme in order to obtain a plurality of entropy encoded values. The residual quantization stage is configured to quantize a residual signal caused by the quantization stage, wherein the residual quantization stage is configured to determine at least one quantized residual value in dependence on the dead zone of the quantization stage. The coded signal former is configured to form a coded signal from the plurality of entropy encoded values and the at least one quantized residual value.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 16/448,511 filed Jun. 21, 2019, which is a continuation of U.S.patent application Ser. No. 15/417,232, filed Jan. 27, 2017, which is acontinuation of copending International Application No.PCT/EP2015/067001, filed Jul. 24, 2015, which is incorporated herein byreference in its entirety, and additionally claims priority fromEuropean Application No. EP 14 178 780.4, filed Jul. 28, 2014,incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Embodiments relate to an encoder, a decoder, a system comprising anencoder and a decoder, a method for encoding and a method for decoding.Some embodiments relate to apparatuses and methods for optimal residualquantization in source coding. Some embodiments relate to a sourcecoding scheme using entropy coding to code a quantized signal on adetermined number of bits.

Entropy coding is an efficient tool for exploiting the redundancy ofsymbols to transmit. It is usually used in transform-based coding afterthe quantization of the spectral lines. By exploiting an a prioriprobability distribution, the quantized values can be losslessly codedwith a reduced number of bits. The principle lies in generatingcodewords for which the length is function of the symbol probability.

The bit consumption is usually only known after writing the entropycoded symbols into the bit stream. It is usually problematic whenoptimizing the quantization stage, which needs to know the bitconsumption for optimizing the rate distortion function. It is even moreproblematic when the bit stream has to have a constant size per frame,also known as constant bitrate, which is a requirement for most of thecommunication network protocols.

In a transform encoder, a set of scale factors defines usually thequantization, by shaping the quantization noise in frequency domain. Thenoise shaping is function of both the perceived distortion, usuallygiven by a psychoacoustic model, and the engendered bit consumption.However the last factor is usually only known after fixing thequantization noise shaping. An optimization loop can be used for makingthe optimization converged. Nevertheless such an optimization isrelatively complex and the number of iterations has to be stronglylimited in real applications. Moreover for reducing even more thecomplexity, the bit consumption is usually not fully computed but onlyestimated. If the final bit consumption is underestimated, thebit-stream will have to be truncated, which is avoided most of the time.Indeed an underestimation will lead to a hard truncation of the bitstream, which is equivalent to make the quantization saturate. Thus, thequantization optimization is usually designed to over-estimate the bitconsumption. As a consequence few bits are often unexploited in thefinal bit stream.

To overcome this problem, a residual (or second) quantization stage canbe added after the first quantization stage for exploiting eventualunused bits. These remaining bits then can be used to refine thequantization noise. This principle is explained in the following.

FIG. 10 shows a block diagram of a transform encoder 10. The transformencoder 10 comprises a first quantization stage 12, a residualquantization stage 14, an entropy encoder 16, an entropy coding bitestimation unit 18, a multiplexer 20 and a transformation unit 22.

The transformation unit 22 is configured to transform an input signalfrom a time domain into a frequency domain. The first quantization stage12 is configured to quantize the input signal in the frequency domaininto a plurality of quantized spectral values q. The plurality ofquantized spectral values q, the input signal in the frequency domain xand a number of remaining bits are input to the residual (or second)quantization stage 14 that is configured to refine the output of thefirst quantization stage 12 and to provide a plurality of quantizedresidual values q_(r). The entropy encoder 16 is configured to entropyencode the plurality of quantized spectral values q in order to obtain aplurality of entropy encoded values e. The multiplexer 20 is configuredto multiplex the plurality of entropy encoded values e, the scalefactors in dependence on an information provided by the firstquantization stage 14 and the plurality of quantized residual valuesdelivered by the second quantization 16 in order to obtain a bit stream.

The transform encoder 10 shown in FIG. 10 is designed for delivering acertain target number of bits per frame. The quantization will beadjusted for reaching this target, but for complexity reasons only anestimation of the entropy encoder bit consumption is done when adjustingthe quantization steps. Moreover even if the bit estimation is veryaccurate it may be impossible to find a set of scale factors which leadto the expected target bits. After the first quantization stage 12,quantized values q are entropy coded. The remaining unexploited bits arethen allocated to the residual quantization which will refine the outputof the first quantization stage 12. The residual quantization stage 14takes as input the quantized spectral values q, the original spectralvalues x and a number of remaining bits. The number of remaining bitscan be an estimate or the true number of remaining bits. The estimate isusually used when a local synthesis is needed at the encoder side fortaking for example a switching decision in a closed-loop decisionfashion as it is done in AMR-WB+ (Adaptive Multi-Rate Wide BandExtended). In that case, the residual coding has to be called before theeventual call of the entropy encoder 16.

In a common transform encoder 10, the residual quantization stage 14performs a simple uniform scalar quantization of the difference of aninverse quantized input signal obtained by inverse quantizing thequantized spectral values and the original input signal. However,through rate-distortion performance analysis, it is known that theuniform quantization is only optimal for memoryless and uniformlydistributed sources.

SUMMARY

According to an embodiment, an encoder may have: a quantization stageconfigured to quantize an input signal using a dead zone in order toobtain a plurality of quantized values; an entropy encoder configured toencode the plurality of quantized values using an entropy encodingscheme in order to obtain a plurality of entropy encoded values; aresidual quantization stage configured to quantize a residual signalcaused by the quantization stage, wherein the residual quantizationstage is configured to determine, for a non-zero quantized value, atleast one quantized residual value in dependence on the dead zone of thequantization stage; and a coded signal former configured to form a codedsignal from the plurality of entropy encoded values and the at least onequantized residual value.

According to another embodiment, a decoder may have: a coded signalparser configured to parse a coded signal in order to obtain a pluralityof entropy encoded values and at least one quantized residual value; anentropy decoder configured to decode the plurality of entropy encodedvalues using an entropy decoding scheme in order to obtain a pluralityof quantized values; and an inverse quantization stage configured toinverse quantize the plurality of quantized values in order to obtain anoutput signal; wherein the inverse quantization stage is configured torefine an inverse quantization level used for obtaining the outputsignal in dependence on the quantized residual value and a dead zone.

According to another embodiment, a system may have: an encoder accordingto the invention; and a decoder according to the invention.

According to another embodiment, a method for encoding may have thesteps of: quantizing an input signal in order to obtain a plurality ofquantized values using a dead zone; encoding the plurality of quantizedvalues using an entropy encoding scheme in order to obtain a pluralityof entropy encoded values; quantizing a residual signal caused by aquantization by the quantization stage and determining a plurality ofquantized residual values in dependence on the dead zone of thequantization stage; and forming a bit stream from the plurality ofentropy encoded values and the plurality of quantized residual values.

According to another embodiment, a method for decoding may have thesteps of: parsing a coded signal in order to obtain a plurality ofentropy encoded values and a quantized residual value; decoding theplurality of entropy encoded values using an entropy decoding scheme inorder to obtain a plurality of quantized values; inverse quantizing theplurality of quantized values in order to obtain an output signal; andrefining an inverse quantization level used for obtaining the outputsignal in dependence on a dead zone and the quantized residual value.

Another embodiment may have a non-transitory digital storage mediumhaving a computer program stored thereon to perform the method forencoding, the method having the steps of: quantizing an input signal inorder to obtain a plurality of quantized values using a dead zone;encoding the plurality of quantized values using an entropy encodingscheme in order to obtain a plurality of entropy encoded values;quantizing a residual signal caused by a quantization by thequantization stage and determining a plurality of quantized residualvalues in dependence on the dead zone of the quantization stage; andforming a bit stream from the plurality of entropy encoded values andthe plurality of quantized residual values, when said computer programis run by a computer.

Another embodiment may have a non-transitory digital storage mediumhaving a computer program stored thereon to perform the method fordecoding, the method having the steps of: parsing a coded signal inorder to obtain a plurality of entropy encoded values and a quantizedresidual value; decoding the plurality of entropy encoded values usingan entropy decoding scheme in order to obtain a plurality of quantizedvalues; inverse quantizing the plurality of quantized values in order toobtain an output signal; and refining an inverse quantization level usedfor obtaining the output signal in dependence on a dead zone and thequantized residual value, when said computer program is run by acomputer.

Embodiments of the present invention provide an encoder comprising aquantization stage, an entropy encoder, a residual quantization stageand a coded signal former. The quantization stage is configured toquantize an input signal using a dead zone in order to obtain aplurality of quantized values. The entropy encoder is configured toencode the plurality of quantized values using an entropy encodingscheme in order to obtain a plurality of entropy encoded values. Theresidual quantization stage is configured to quantize a residual signalcaused by the quantization stage, wherein the residual quantizationstage is configured to determine at least one quantized residual valuein dependence on the dead zone of the quantization stage. The codedsignal former is configured to form a coded signal from the plurality ofentropy encoded values and the at least one quantized residual value.

Further, embodiments of the present invention provide a decodercomprising a coded signal parser, an entropy decoder and an inversequantization stage. The coded signal parser is configured to parse acoded signal in order to obtain a plurality of entropy encoded valuesand at least one quantized residual value. The entropy decoder isconfigured to decode the plurality of entropy encoded values using anentropy decoding scheme in order to obtain a plurality of quantizedvalues. The inverse quantization stage is configured to inverse quantizethe plurality of quantized values in order to obtain an output signal.Further, the inverse quantization stage is configured to refine aninverse quantization level used for obtaining the output signal independence on the quantized residual value and a dead zone.

According to the concept of the present invention, an error between the(original) input signal and an inverse quantized signal obtained byinverse quantizing the plurality of quantized values can be reduced oreven optimized by a residual quantization stage at the encoder side thattakes into account the dead zone which was used for quantizing the inputsignal and an inverse quantization stage at the decoder side that alsotakes into account this dead zone when refining the inverse quantizationlevel used for obtaining the inverse quantized signal (referred to asoutput signal).

Furthermore, embodiments of the present invention provide a method forencoding. The method comprises quantizing an input signal in order toobtain a plurality of quantized values using a dead zone; encoding theplurality of quantized values using an entropy encoding scheme in orderto obtain a plurality of entropy encoded values; quantizing a residualsignal caused by a quantization by the quantization stage anddetermining a plurality of quantized residual values in dependence onthe dead zone of the quantization stage; and forming a bit stream fromthe plurality of entropy encoded values and the plurality of quantizedresidual values.

Moreover, embodiments of the present invention provide a method fordecoding, the method comprises parsing a coded signal in order to obtaina plurality of entropy encoded values and a quantized residual value;decoding the plurality of entropy encoded values using an entropydecoding scheme in order to obtain a plurality of quantized values;inverse quantizing the plurality of quantized values using a dead zonein order to obtain an output signal; and refining an inversequantization level used for obtaining the output signal in dependence ona dead zone and the quantized residual value.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 shows a block diagram of an encoder according to an embodiment ofthe present invention.

FIG. 2 shows a block diagram of a decoder according to an embodiment ofthe present invention.

FIG. 3 shows a block diagram of a system according to an embodiment ofthe present invention.

FIG. 4 shows a block diagram of the residual quantization stageaccording to an embodiment of the present invention.

FIG. 5 shows in a diagram inverse quantization levels and quantizationthresholds used in a dead zone uniform threshold scalar quantizationscheme.

FIG. 6 shows in a diagram two refined inverse quantization levels for anon-zero quantized value.

FIG. 7 shows in a diagram three refined inverse quantization levels fora zero quantized value.

FIG. 8 shows a flowchart of a method for encoding according to anembodiment of the present invention.

FIG. 9 shows a flowchart of a method for decoding according to anembodiment of the present invention.

FIG. 10 shows a block diagram of a conventional transform encoder usinga residual quantization.

DETAILED DESCRIPTION OF THE INVENTION

Equal or equivalent elements or elements with equal or equivalentfunctionality are denoted in the following description by equal orequivalent reference numerals.

In the following description, a plurality of details are set forth toprovide a more thorough explanation of embodiments of the presentinvention. However, it will be apparent to those skilled in the art thatembodiments of the present invention may be practiced without thesespecific details. In other instances, well-known structures and devicesare shown in block diagram form rather than in detail in order to avoidobscuring embodiments of the present invention. In addition, features ofthe different embodiments described hereinafter may be combined witheach other, unless specifically noted otherwise.

Since entropy coding delivers variable length code-words, it isdifficult to predict the exact bit consumption before writing thebit-stream. However the bit consumption is needed for optimizing thequantization. Most of the time and for complexity reasons, thequantization is suboptimal and some few bits are still unexploited.Residual quantization is a second layer of quantization which exploitsthese unused bits for refining the quantization error.

The below described embodiments of the present invention provide anencoder, a decoder and methods which optimize this residualquantization.

FIG. 1 shows a block diagram of an encoder 100 according to anembodiment of the present invention. The Encoder 100 comprises aquantization stage 102 (e.g., a first quantization stage), an entropyencoder 104, a residual quantization stage 106 (e.g., a secondquantization stage) and a coded signal former 108. The quantizationstage 102 is configured to quantize an input signal 140 using a deadzone in order to obtain a plurality of quantized values 142 (q). Theentropy encoder 104 is configured to encode the plurality of quantizedvalues 142 (q) using an entropy encoding scheme in order to obtain aplurality of entropy encoded values 144 (e). The residual quantizationstage 106 is configured to quantize a residual signal caused by aquantization in the quantization stage 102, wherein the residualquantization stage 106 is configured to determine at least one quantizedresidual value 146 (q_(r)) in dependence on the dead zone of thequantization stage 102. The coded signal former 108 is configured toform a coded signal 148 from the plurality of entropy encoded values 144(e) and the at least one quantized residual value 146 (q_(r)).

The idea of the present invention is to reduce or even optimize theerror between the (original) input signal and an inverse quantizedversion of a quantized version of the input signal by a residualquantization stage at the encoder side that takes into account the deadzone which was used for quantizing the input signal and an inversequantization stage at the decoder side that also takes into account thisdead zone when refining the inverse quantization level used forobtaining the inverse quantized signal.

In embodiments, the quantization stage 102 can be configured to performa dead zone uniform threshold scalar quantization (DZ-UTSQ).

In embodiments, the coded signal former 108 can be configured to formthe coded signal 148 by appending the at least one quantized residualvalue 146 or a plurality of quantized residual values 146 to theplurality of entropy encoded values 144 until the coded signal 148comprises a maximum length available for a transfer to a decoder. It isnot restricted that the bit-stream contains other information as scalefactors defining the first quantization stage noise shaping, orprediction coefficients used for shaping the quantization noise and usedin a post-filtering of the output signal in tie domain.

For example, the coded signal former 108 may be configured to provide abit stream as the coded signal 148. Thereby, the coded signal former108, for example, a multiplexer, can be configured to add at an end ofthe bit stream the at least one quantized residual value 146 or aplurality of quantized residual values 146. The bit stream generated bythe encoder 100 may be transferred (e.g., transmitted or broadcasted) toa decoder or may be stored, for example, on a non-volatile storagemedium, for a later decoding by a decoder. Thereby, the bit stream maybe transmitted or stored using data frames or data packets, wherein thebit stream may have to have a constant size (also referred herein astarget bits) per data frame or data packet.

For obtaining a bit stream having a constant size or a predefined numberof target bits the coded signal former 108 may be configured to appendquantized residual values 146 to the entropy encoded values 144 untilthe bit stream reaches the predefined number of target bits. Theresidual quantization stage 106 may stop determining quantized residualvalues 146 when the bit stream comprises the predefined length or numberof target bits.

In embodiments, the input signal 140 can be a frequency domain inputsignal 140. The encoder 100 can comprise a transformation unitconfigured to transform a time domain input signal into the frequencydomain input signal 140.

FIG. 2 shows a block diagram of a decoder 120 according to an embodimentof the present invention. The decoder 120 comprises a coded signalparser 122, an entropy decoder 124 and an inverse quantization stage126. The coded signal parser 122 is configured to parse a coded signal148 in order to obtain a plurality of entropy encoded values 144 (e) andat least one quantized residual value 146 (q_(r)). The entropy decoder124 is configured to decode the plurality of entropy encoded values 144(e) using an entropy decoding scheme in order to obtain a plurality ofquantized values 142 (q). The inverse quantization stage 126 isconfigured to inverse quantize the plurality of quantized values 142 (q)in order to obtain an output signal 150. Thereby, the inversequantization stage 126 is configured to refine an inverse quantizationlevel used for obtaining the output signal 150 in dependence on thequantized residual value 146 (q_(r)) and a dead zone used in an encoder100 in a quantization stage 106 for obtaining the plurality of quantizedvalues 142 (q).

In embodiments, the inverse quantization stage 126 can be configured torefine the inverse quantization level by determining a refined inversequantization level in dependence on the dead zone.

For example, the inverse quantization stage 126 may be configured todetermine in dependence on the dead zone, or more precisely, independence on a width of the dead zone, a level by which the inversequantization level has to be refined, i.e. increased or decreased, inorder to obtain the refined inverse quantization level. Further, theinverse quantization stage 126 may be configured to determine at leasttwo new inverse quantization levels in dependence on the dead zone, andto obtain the output signal 150 by using one out of the at least tworefined inverse quantization levels indicated by quantized residualvalue 146. In other words, the quantized residual value 146 indicateswhich out of the at least two refined inverse quantization levels is tobe used for obtaining the output signal 150.

FIG. 3 shows a block diagram of a system 130 according to an embodimentof the present invention. The system 130 comprises the encoder 100 shownin FIG. 1 and the decoder 120 shown in FIG. 2.

In the following, features of the encoder 100 and decoder 120 and thecoaction or interaction of features of the encoder 100 and decoder 120are described in further detail.

FIG. 4 shows a block diagram of the residual quantization stage 106according to an embodiment. The residual quantization stage 106 maycomprise a residual quantizer 106′, an inverse quantizer 160 and acomparer 162. The inverse quantizer 160 can be configured to inversequantize the plurality of quantized values 142 (q) provided by thequantization stage 102 in order to obtain an inverse quantized inputsignal 152 (x_q). The comparison stage 162 can be configured to comparethe input signal 140 (x) and the inverse quantized input signal 152(x_q) in order to obtain the residual signal 154. The residual quantizer106′ can be configured to quantize the residual signal caused by thequantization stage 102.

In other words, the residual quantization block diagram is illustratedin FIG. 4. The spectrum 142 (q) is inversely quantized and compared tothe original spectrum 140 (x). A second layer of quantization is thenperformed depending of the remaining bits available. The secondquantization step performed by the residual quantization stage 106 isusually a greedy quantization, i.e. that the quantization is performedline per line and each re-quantized value is done independently from thefollowing transmitted information. In that way the residual quantizationbit-stream 146 (q_(r)) can be truncated whenever the bit-stream 148provided by the coded signal former 108 reaches the desired size.

As shown in FIG. 4, the residual quantization stage 106 may furthercomprise a control unit 164, e.g., an adjuster. The control unit 164 maybe configured to control or optimize the residual quantizer 106′.

For example, the control unit 164 may be configured to control theresidual quantizer 106′ such that the residual quantizer 106′ quantizesthe residual signal 154 in dependence on the dead zone, or moreprecisely, in dependence on a width of the dead zone used in thequantization stage 102 for obtaining the plurality of quantized values142 (q). Further, the control unit 164 may be configured to control theresidual quantizer 106′ in dependence on a number of target bits and anumber of consumed bits (e.g., consumed by the entropy encoded values144 provided by the entropy encoder or by the entropy encoded values 144and the quantized residual value(s) already provided by the residualquantizer 106′). Further, the control unit 164 may be configured tocontrol the residual quantizer 106′ in dependence on an informationprovided by the inverse quantizer 160. The information provided by theinverse quantizer 160 may include the width of the dead zone, which canbe either fixed and modified adaptively, and may also include a scalefactor applied in the first quantization stage for normalizing thespectrum and defining the quantization step, and may also include anindication if the quantized value was zeroed or not.

In a conventional residual quantization, Qr performed by the residualquantization stage is a simple uniform scalar quantization of thedifference x[i]-x_q[i]:

if x[i]>x_q[i]

Qr[i]=(int)(0.5+(x[i]−x_q[i])/delta_r)

Else

Qr[i]=(int)(−0.5+(x[i]−x_q[i])/delta_r)

wherein x[i] is the input signal 140, wherein x_Q[i] is the inversequantized input signal 152, wherein (int) is an integer roundingfunction, and wherein delta_r is the quantization step of the residualquantizer Qr which is usually smaller that the quantization step deltaused in the first quantizer Q. In general:

delta_r=0.5*delta

Embodiments of the present invention solve two problems related to theresidual quantization. The first and main problem is how to get theoptimal Qr (function of the residual quantization stage 106) knowing thefirst quantization stage 102. The second problem is how to minimize themismatch between the encoder local synthesis and the decoder synthesis,when the number of remaining bits has to be estimated.

Through rate-distortion performance analysis, it is know that theuniform quantization (as used in a conventional residual quantization)is only optimal for memoryless and uniformly distributed sources. If anentropy coding is used afterwards, the uniform quantization is quasioptimal for a Gaussian source and at very high bit-rates. At lower ratesthe near optimal solution is to have a dead zone with uniform thresholdscalar quantization (DZ-UTSQ). This family of quantizers is quasioptimal for a large range of distributions, e.g. Gaussian, Laplacian andgeneralized Laplacian. The dead zone factor can be optimized bydifferent methods. It can be optimized in real time depending onestimate of the distribution. Simplier it can be fixed to a default bestvalue found for expected input signals or adapted depending on somemeasures, like the tonality of the spectrum, which reflects also thedistribution.

In the following, a solution to optimize the residual quantization Qrperformed by the residual quantization stage 106 depending on a firststage DZ-UTSQ 102 is presented. The dead zone parameter is called dz andDZ-UTSQ 102 is defined as:

if x[i]>0

Q[i]=(int)(rounding_dz+(x[i])/delta)

Else

Q[i]=(int)(−rounding_dz+(x[i])/delta)

and

x_q[i]=delta*Q[i]

wherein x[i] is the input signal 140, wherein x_Q[i] is the inversequantized input signal 152, wherein (int) is an integer roundingfunction, and wherein delta is the quantization step used in DZ-UTSQ102, and wherein rounding_dz=1−dz/2.

FIG. 5 illustrates the DZ-UTSQ 102 scheme, where the scale is normalizedby delta. The dead zone is usually larger than the normalized cell sizeof step 1. A dead zone of 1.25 is a good estimate for most of thefrequency transformed audio samples. It can be reduced if the signal isnoisier and enlarged when it is more tonal.

Embodiments of the present invention define the optimal quantizationrefinement of the error x[i]−x_q[i]. Because the residual coding is notentropy constrained no additional dead zone is adopted in the residualquantization Qr. Moreover, the distribution of the quantization error ofthe first quantization stage 102 is assumed to be uniform in left andright parts of the quantization cell delimited by the reconstructionlevel 170. It is a high-rate assumption, i.e. the size of the newquantization cells are considered small enough for discarding non-evendistributed errors within the cell. The assumption is valid for most ofthe target bit-rates.

There are two main cases: a sample was quantized with a non-zero valueand a sample was quantized with a zero value.

For a non-zero quantized value, 1 bit can be allocated for the residualquantization Qr per sample and define two relative reconstruction levelsfac_m and fac_p:

fac_p=0.5−rounding_dz*0.5=0.25*(dz)

fac_m=0.5*rounding_dz=0.5*(1−0.5*dz)

Thereby, fac_p may indicate a normalized absolute value by which anormalized absolute value of the inverse quantization level (orreconstruction level) 172 is to be increased in order to obtain a firstrefined inverse quantization level 174 of the two refined inversequantization levels 174 and 176, wherein fac_m indicates a normalizedabsolute value by which the normalized absolute value of the inversequantization level 172 is to be decreased in order to obtain a secondrefined inverse quantization level 176 of the two refined inversequantization levels 174 and 176, and wherein dz is a normalized width ofthe dead zone, as will become clear from FIG. 6

FIG. 6 illustrates the two relative (or refined) reconstructive levels174 and 176 for a reconstruction level 172 of 1. With 1 bit additionalbit, the reconstruction level 172 can be refined with 1−fac_m (leadingto the second refined inverse quantization level 176) or with 1+fac_p(leading to the first refined inverse quantization level 174). Theoriginal cell is split into two non-uniform cells. Because thequantization error of Q (quantization function of the first quantizationstage 102) is assumed to be uniformly distributed within the new cells,the residual quantization Qr is optimal in terms of R-D performance.Please note that the quantization Q and the residual quantization Qrform an embedded quantization, i.e. the bit allocated to the residualquantization Qr can be discarded and still Q−1 can be performed.

The residual quantization Qr performed by the residual quantizationstage 106 can be summarized by:

${pr{m\lbrack n\rbrack}} = \left\{ \begin{matrix}{{0\mspace{14mu} {if}\mspace{14mu} {x\lbrack i\rbrack}} < {x_{-}{Q\lbrack i\rbrack}}} \\{1\mspace{14mu} {otherwise}}\end{matrix} \right.$

wherein prm is a bit stream generated by the residual quantization stage106 using the quantized residual value, wherein x[i] is the inputsignal, wherein x_Q[i] is the inverse quantized input signal, wherein nis an index that is incremented by 1 for each non-zero quantized valuewhich is refined by Q_(r), and wherein i is an index that is incrementedby 1 for each obtained quantized value.

The inverse Qr can be then expressed as:

if  (x_Q[i] > 0&n < N_(bits))  then${{x\_ Q}\lbrack i\rbrack} = \left\{ {{\begin{matrix}{{{{x\_ Q}\lbrack i\rbrack} - {{delta}*{fac\_ m}\mspace{14mu} {if}\mspace{14mu} {{prm}\lbrack n\rbrack}}} = 0} \\{{{x\_ Q}\lbrack i\rbrack} + {{delta}*{fac\_ p}\mspace{14mu} {otherwise}}}\end{matrix}{else}\mspace{14mu} {if}\mspace{14mu} \left( {n < N_{bits}} \right)\mspace{14mu} {then}{{x\_ Q}\lbrack i\rbrack}} = \left\{ \begin{matrix}{{{{x\_ Q}\lbrack i\rbrack} - {{delta}*{fac\_ p}\mspace{14mu} {if}\mspace{14mu} {{prm}\lbrack n\rbrack}}} = 0} \\{{{x\_ Q}\lbrack i\rbrack} + {{delta}*{fac\_ m}\mspace{14mu} {otherwise}}}\end{matrix} \right.} \right.$

It can be seen that the inverse Qr is only performed for N_(bits) firstbits. That means that the encoder can generate more bits than theencoder or decoder will actually decode. This mechanism is used when theremaining number of bits is estimated and when the local synthesis atthe encoder side needs to generated. The expected reconstructed signalis generated at the encoder although it is possible for the decoder todecode more or less bits depending of the true remaining available bitsin the bit stream.

Alternatively, more than 1 bit can be allocated per sample to Qr. Withthe same principle the optimal reconstruction levels for 2 power of bitsQr reconstruction levels can be defined.

For a zero quantized value, the residual quantization Qr can beallocated with more than 1 bit. The reason is that for perceptualreason, zero as a reconstruction level is needed. It avoids for examplecreating an artificial noisy signal during silence. A special 3 levelsvariable length code can be used:

0: code a zero10: a negative reconstruction level11: a positive reconstruction level

A new relative reconstruction level is computes, fac_z:

fac_z=dz/3

Thereby fac_z may indicate a normalized absolute value by which anormalized absolute value of the inverse quantization level 172 is to beincreased in order to obtain a first refined inverse quantization level174 of the two refined inverse quantization levels 174 and 176 and anormalized absolute value by which a normalized absolute value of theinverse quantization level is to be decreased in order to obtain asecond refined inverse quantization level 176 of the two refined inversequantization levels 174 and 176, and wherein dz is a normalized width ofthe dead zone, as will become clear from FIG. 7.

FIG. 7 illustrates the residual quantization Qr performed by theresidual quantization stage 106 for a zero quantized values 142. Thecell around zero is divided in three uniform new cells.

The residual quantization Qr performed by the residual quantizationstage 106 for a zero quantized value can be summarized by

${pr{m\lbrack n\rbrack}} = \left\{ {{{\begin{matrix}{{0\mspace{14mu} {if}\mspace{14mu} {{x\lbrack i\rbrack}}} < \left( {C \cdot {{x\_ Q}\lbrack i\rbrack}} \right)} \\{1\mspace{14mu} {otherwise}}\end{matrix}{if}\mspace{14mu} {{prm}\lbrack n\rbrack}}=={1\mspace{14mu} {then}{pr}{m\left\lbrack {n + 1} \right\rbrack}}} = \left\{ \begin{matrix}{{0\mspace{14mu} {if}\mspace{14mu} {x\lbrack i\rbrack}} < 0} \\{1\mspace{14mu} {otherwise}}\end{matrix} \right.} \right.$

wherein C depends on the dead zone of the quantization stage and may becalculated to C=delta*(fac_z/2), wherein prm is a bit stream generatedby the residual quantization stage 106 using the quantized residualvalue, wherein x[i] is the input signal, wherein x_Q[i] is the inversequantized input signal. The index n is incremented by 1 for each zeroquantized value requantized to zero, wherein n is incremented by 2 foreach zero quantized value requantized to a non-zero value.

The inverse Qr can be then expressed as:

if  (n < N_(bits))  then${{x\_ Q}\lbrack i\rbrack} = \left\{ \begin{matrix}{{{delta}*{fac\_ z}\mspace{14mu} {if}\mspace{14mu} {{prm}\lbrack n\rbrack}} = {{{1\&}{pr}{m\left\lbrack {n + 1} \right\rbrack}} = 1}} \\{{{- {delta}}*{fac\_ z}\mspace{14mu} {if}\mspace{14mu} {{prm}\lbrack n\rbrack}} = {{{1\&}{pr}{m\left\lbrack {n + 1} \right\rbrack}} = 0}} \\{0\mspace{14mu} {otherwise}}\end{matrix} \right.$

Embodiments of the present invention can easily be extended with theassumption that the distribution within the original quantization cellis not uniform. In this case, the relative reconstruction levels can bederived depending on the distribution of the quantization error. A wayof achieving it is to split the original quantization cell intonon-uniform new smaller cells.

A second dead zone parameter can be used as well.

In the following, further embodiments of the encoder 100 and decoder 120are briefly described.

First, the encoder 100 is described.

The residual quantization is a refinement quantization layer refiningthe first SQ stage (or quantization stage 102). It exploits eventualunused bits, i.e. unused bits=target_bits-nbbits, where nbbits is thenumber of bits consumed by the entropy coder 104. The residualquantization adopts a greedy strategy and no entropy in order to stopthe coding whenever the bit stream reaches the desired size.

The refinement consists of re-quantizing the quantized spectrum line perline. First, the non-zero quantized lines are processed with a 1 bitresidual quantizer:

if (X[k]<{circumflex over (X)}[k]) then

-   -   write_bit(0)        else then    -   write_bit(1)

Thereby, X[k] is a scaled sample of the input signal 140 andX[{circumflex over (k)}] is the scaled corresponding sample of theinverse quantized input signal 152.

Finally, if remaining bits allow, the zero quantized lines areconsidered and quantized with on 3 levels as follows:

fac_z=(1—rounding_dz)·0.66if(|X[k]|<0.5·fac_z·{circumflex over (X)}[k]) then

-   -   write_bit(0)        else then    -   write_bit(1)    -   write_bit((1+sgn(X[k]))/2)

Thereby, X[k] is a scaled sample of the input signal 140, X[{circumflexover (k)}] is the corresponding scaled sample of the inverse quantizedinput signal 152, fac_z may indicate a normalized absolute value bywhich a normalized absolute value of the inverse quantization level 172is to be increased in order to obtain a first refined inversequantization level 174 of the two refined inverse quantization levels174 and 176 and a normalized absolute value by which a normalizedabsolute value of the inverse quantization level is to be decreased inorder to obtain a second refined inverse quantization level 176 of thetwo refined inverse quantization levels 174 and 176, whereinrounding_dz=1−dz/2.

Second, the decoder 120 is described.

The remaining bits refine the non-zero decoded lines. 1 bit per non-zerospectral value is read:

fac_p = (1 − rounding_dz)/2 fac_m = rounding_dz/2if  (read_bit() =  = 0)  then${\hat{X}\lbrack k\rbrack} = \left\{ {{\begin{matrix}{{{\hat{X}\lbrack k\rbrack} - {{fac\_ m}\mspace{14mu} {if}\mspace{14mu} {\hat{X}\lbrack k\rbrack}}} > 0} \\{{\hat{X}\lbrack k\rbrack} - {{fac\_ p}\mspace{14mu} {otherwise}}}\end{matrix}{else}\mspace{14mu} {then}{\hat{X}\lbrack k\rbrack}} = \left\{ \begin{matrix}{{{\hat{X}\lbrack k\rbrack} + {{fac\_ p}\mspace{14mu} {if}\mspace{14mu} {\hat{X}\lbrack k\rbrack}}} > 0} \\{{\hat{X}\lbrack k\rbrack} + {{fac\_ m}\mspace{14mu} {otherwise}}}\end{matrix} \right.} \right.$

Thereby, X[k] is the input signal 140, X[{circumflex over (k)}] is theinverse quantized input signal 152, fac_p may indicate a normalizedabsolute value by which a normalized absolute value of the inversequantization level (or reconstruction level) 172 is to be increased inorder to obtain a first refined inverse quantization level 174 of thetwo refined inverse quantization levels 174 and 176, and fac_m mayindicate a normalized absolute value by which the normalized absolutevalue of the inverse quantization level 172 is to be decreased in orderto obtain a second refined inverse quantization level 176 of the tworefined inverse quantization levels 174 and 176, whereinrounding_dz=1−dz/2

If at least 2 bits are left to read, a zero value is refined as:

fac_z=(1−rounding_dz)·0.66if (read_bit( )==0) then

-   -   {circumflex over (X)}[k]=0        else then    -   if (read_bit( )==0) then        -   {circumflex over (X)}[k]=−fac_z    -   else then        -   {circumflex over (X)}[k]=fac_z

Thereby, X[k] is a scaled sample of the input signal 140, X[{circumflexover (k)}] is the corresponding scaled sample of the inverse quantizedinput signal 152, fac_z may indicate a normalized absolute value bywhich a normalized absolute value of the inverse quantization level 172is to be increased in order to obtain a first refined inversequantization level 174 of the two refined inverse quantization levels174 and 176 and a normalized absolute value by which a normalizedabsolute value of the inverse quantization level is to be decreased inorder to obtain a second refined inverse quantization level 176 of thetwo refined inverse quantization levels 174 and 176, whereinrounding_dz=1−dz/2.

FIG. 8 shows a flow chart of a method for encoding 200 according to anembodiment. The method 200 comprises a step 202 of quantizing an inputsignal in order to obtain a plurality of quantized values using a deadzone; a step 204 of encoding the plurality of quantized values using anentropy encoding scheme in order to obtain a plurality of entropyencoded values; a step 206 of quantizing a residual signal caused by aquantization by the quantization stage and determining a plurality ofquantized residual values in dependence on the dead zone of thequantization stage; and a step 208 of forming a bit stream from theplurality of entropy encoded values and the plurality of quantizedresidual values.

FIG. 9 shows a flow chart of a method for decoding 220 according to anembodiment. The method 220 comprises a step 222 of parsing a codedsignal in order to obtain a plurality of entropy encoded values and aquantized residual value; a step 224 of decoding the plurality ofentropy encoded values using an entropy decoding scheme in order toobtain a plurality of quantized values; a step 226 of inverse quantizingthe plurality of quantized values using a dead zone in order to obtainan output signal; and a step 228 of refining an inverse quantizationlevel used for obtaining the output signal in dependence on a dead zoneand the quantized residual value.

Although some aspects have been described in the context of anapparatus, it is clear that these aspects also represent a descriptionof the corresponding method, where a block or device corresponds to amethod step or a feature of a method step. Analogously, aspectsdescribed in the context of a method step also represent a descriptionof a corresponding block or item or feature of a correspondingapparatus. Some or all of the method steps may be executed by (or using)a hardware apparatus, like for example, a microprocessor, a programmablecomputer or an electronic circuit. In some embodiments, some one or moreof the most important method steps may be executed by such an apparatus.

Depending on certain implementation requirements, embodiments of theinvention can be implemented in hardware or in software. Theimplementation can be performed using a digital storage medium, forexample a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM,an EEPROM or a FLASH memory, having electronically readable controlsignals stored thereon, which cooperate (or are capable of cooperating)with a programmable computer system such that the respective method isperformed. Therefore, the digital storage medium may be computerreadable.

Some embodiments according to the invention comprise a data carrierhaving electronically readable control signals, which are capable ofcooperating with a programmable computer system, such that one of themethods described herein is performed.

Generally, embodiments of the present invention can be implemented as acomputer program product with a program code, the program code beingoperative for performing one of the methods when the computer programproduct runs on a computer. The program code may for example be storedon a machine readable carrier.

Other embodiments comprise the computer program for performing one ofthe methods described herein, stored on a machine readable carrier.

In other words, an embodiment of the inventive method is, therefore, acomputer program having a program code for performing one of the methodsdescribed herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a datacarrier (or a digital storage medium, or a computer-readable medium)comprising, recorded thereon, the computer program for performing one ofthe methods described herein. The data carrier, the digital storagemedium or the recorded medium are typically tangible and/ornon-transitionary.

A further embodiment of the inventive method is, therefore, a datastream or a sequence of signals representing the computer program forperforming one of the methods described herein. The data stream or thesequence of signals may for example be configured to be transferred viaa data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example acomputer, or a programmable logic device, configured to or adapted toperform one of the methods described herein.

A further embodiment comprises a computer having installed thereon thecomputer program for performing one of the methods described herein.

A further embodiment according to the invention comprises an apparatusor a system configured to transfer (for example, electronically oroptically) a computer program for performing one of the methodsdescribed herein to a receiver. The receiver may, for example, be acomputer, a mobile device, a memory device or the like. The apparatus orsystem may, for example, comprise a file server for transferring thecomputer program to the receiver.

In some embodiments, a programmable logic device (for example a fieldprogrammable gate array) may be used to perform some or all of thefunctionalities of the methods described herein. In some embodiments, afield programmable gate array may cooperate with a microprocessor inorder to perform one of the methods described herein. Generally, themethods are performed by any hardware apparatus.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and compositions of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutationsand equivalents as fall within the true spirit and scope of the presentinvention.

1. An encoder, comprising: a quantization stage configured to quantizean input signal using a dead zone in order to obtain a plurality ofquantized values; an entropy encoder configured to encode the pluralityof quantized values using an entropy encoding scheme in order to obtaina plurality of entropy encoded values; a residual quantization stageconfigured to quantize a residual signal caused by the quantizationstage, wherein the residual quantization stage is configured todetermine, for a non-zero quantized value, at least one quantizedresidual value in dependence on the dead zone of the quantization stage;and a coded signal former configured to form a coded signal from theplurality of entropy encoded values and the at least one quantizedresidual value.
 2. The encoder according to claim 1, wherein theresidual quantization stage is configured to determine, for a non-zeroquantized value, at least one quantized residual value in dependence ona width of the dead zone of the quantization stage.
 3. The encoderaccording to one claim 1, wherein the residual quantization stagecomprises: an inverse quantizer configured to inverse quantize theplurality of quantized values in dependence on the dead zone of thequantization stage in order to obtain an inverse quantized input signal;wherein the residual quantization stage is configured to determine theat least one quantized residual value such that the quantized residualvalue comprises 1 bit for a non-zero quantized value; and wherein theresidual quantization stage is configured to determine, for the non-zeroquantized value, that the quantized residual value comprises a logic 0if the input signal is smaller than the inverse quantized input signalfor the non-zero quantized value, and to determine, for the non-zeroquantized value, that the quantized residual value comprises a logic 1else.
 4. The encoder according to claim 1, wherein the residualquantization stage comprises: an inverse quantizer configured to inversequantize the plurality of quantized values in dependence on the deadzone in order to obtain an inverse quantized input signal; and acomparer configured to compare the input signal and the inversequantized input signal.
 5. The encoder according to claim 4, wherein thecomparer is configured to compare the input signal and the inversequantized input signal in order to obtain the residual signal; whereinthe residual quantization stage is configured to quantize the residualsignal in dependence on the dead zone.
 6. The encoder according to claim5, wherein the residual quantization stage is configured to determinethe at least one quantized residual value such that the quantizedresidual value comprises 1 bit for a non-zero quantized value; andwherein the residual quantization stage is configured to determine, forthe non-zero quantized value, that the quantized residual valuecomprises a logic 0 if the residual signal is negative for the non-zeroquantized value, and to determine, for the non-zero quantized value,that the quantized residual value comprises a logic 1 else.
 7. Theencoder according to claim 1, wherein the residual quantization stage isconfigured to determine the at least one quantized residual value suchthat the quantized residual value comprises 1 bit for a non-zeroquantized value, wherein the residual quantization stage is configuredto determine the quantized residual value based on the syntax${pr{m\lbrack n\rbrack}} = \left\{ \begin{matrix}{{0\mspace{14mu} {if}\mspace{14mu} {x\lbrack i\rbrack}} < {{x\_ Q}\lbrack i\rbrack}} \\{1\mspace{14mu} {otherwise}}\end{matrix} \right.$ wherein prm is a bit stream generated by theresidual quantization stage using the quantized residual value, whereinx[i] is the input signal 140, wherein x_Q[i] is the inverse quantizedinput signal, wherein n is an index that is incremented by 1 for eachnon-zero quantized value, and wherein i is an index that is incrementedby 1 for each obtained quantized value.
 8. The encoder according toclaim 1, wherein the residual quantization stage is configured todetermine the quantized residual value such that the quantized residualvalue comprises 2 bits for a zero quantized value, wherein the residualquantization stage is configured to determine the quantized residualvalue based on the syntax${pr{m\lbrack n\rbrack}} = \left\{ {{{\begin{matrix}{{0\mspace{14mu} {if}\mspace{14mu} {{x\lbrack i\rbrack}}} < \left( {C \cdot {{x\_ Q}\lbrack i\rbrack}} \right)} \\{1\mspace{14mu} {otherwise}}\end{matrix}{if}\mspace{14mu} {{prm}\lbrack n\rbrack}}=={1\mspace{14mu} {then}{{prm}\left\lbrack {n + 1} \right\rbrack}}} = \left\{ \begin{matrix}{{0\mspace{14mu} {if}\mspace{14mu} {x\lbrack i\rbrack}} < 0} \\{1\mspace{14mu} {otherwise}}\end{matrix} \right.} \right.$ wherein C depends on the dead zone of thequantization stage, wherein prm is a bit stream generated by theresidual quantization stage using the quantized residual value, whereinx[i] is the input signal, wherein x_Q[i] is the inverse quantized inputsignal, wherein n is an index that is incremented by 1 for each zeroquantized value that is requantized to a zero quantized value andincremented by 2 for each zero quantized value that is requantized to anon-zero quantized value, and wherein i is an index that is incrementedby 1 for each obtained quantized value.
 9. The encoder according toclaim 1, wherein the coded signal former is configured to form the codedsignal by appending the at least one quantized residual value or aplurality of quantized residual values to the plurality of entropyencoded values until the coded signal comprises a maximum lengthavailable for a transfer to a decoder.
 10. The encoder according toclaim 1, wherein the coded signal former is configured to provide a bitstream as the coded signal, wherein the coded signal former isconfigured to form the bit stream from the plurality of entropy encodedvalues and the plurality of quantized residual values, wherein the codedsignal former is configured to append the quantized residual values tothe entropy encoded values, wherein the residual quantization stagecomprises: a residual quantizer; and an adjuster configured to controlthe residual quantizer to quantize the residual signal in dependence ona width of the dead zone used in the quantization stage for obtainingthe plurality of quantized values; wherein the adjuster is configured toobtain a number of target bits and a number of consumed bits; andwherein the adjuster is configured to control the residual quantizationstage to stop determining quantized residual values when the bit streamcomprises the number of target bits.
 11. A decoder, comprising: a codedsignal parser configured to parse a coded signal in order to obtain aplurality of entropy encoded values and at least one quantized residualvalue; an entropy decoder configured to decode the plurality of entropyencoded values using an entropy decoding scheme in order to obtain aplurality of quantized values; and an inverse quantization stageconfigured to inverse quantize the plurality of quantized values inorder to obtain an output signal; wherein the inverse quantization stageis configured to refine an inverse quantization level used for obtainingthe output signal in dependence on the quantized residual value and adead zone.
 12. The decoder according to claim 11, wherein the inversequantization stage is configured to refine an inverse quantization levelfor a non-zero quantized value in dependence on a quantized residualvalue and a width of the dead zone.
 13. The decoder according to claim11, wherein the inverse quantization stage is configured to refine theinverse quantization level by determining a refined inverse quantizationlevel in dependence on the dead zone.
 14. The decoder according to claim13, wherein the inverse quantization stage is configured to determinetwo refined inverse quantization levels for a non-zero quantized value,wherein the inverse quantization stage is configured to obtain theoutput signal by using one out of the two refined inverse quantizationlevels indicated by quantized residual value.
 15. The decoder accordingto claim 14, wherein the inverse quantization stage is configured toincrease a normalized absolute value of the inverse quantization levelby an increase value in order to obtain a first of the two refinedinverse quantization levels; wherein the inverse quantization stage isconfigured to decrease a normalized absolute value of the inversequantization level by a decrease value in order to obtain a second ofthe two refined inverse quantization levels; and wherein the increasevalue and the decrease value are different from each other.
 16. Thedecoder according to claim 14, wherein the inverse quantization stage isconfigured to determine the two refined inverse quantization levels fora non-zero quantized value based on the two factors:fac_p=0.25*dzfac_m=0.5*(1−0.5*dz) wherein fac_p indicates a normalized absolute valueby which a normalized absolute value of the inverse quantization levelis to be increased in order to obtain a first of the two refined inversequantization levels, wherein fac_m indicates a normalized absolute valueby which the normalized absolute value of the inverse quantization levelis to be decreased in order to obtain a second of the two refinedinverse quantization levels, and wherein dz is a normalized width of thedead zone.
 17. The decoder according to claim 13, wherein the inversequantization stage is configured to determine two refined inversequantization levels for a zero quantized value, wherein the inversequantization stage is configured to obtain the output signal by usingone out of the inverse quantization level and two refined inversequantization levels indicated by quantized residual value.
 18. Thedecoder according to claim 17, wherein the inverse quantization stage isconfigured to increase a normalized absolute value of the inversequantization level by an increase value in order to obtain a first ofthe two refined inverse quantization levels; wherein the inversequantization stage is configured to decrease a normalized absolute valueof the inverse quantization level by a decrease value in order to obtaina second of the two refined inverse quantization levels.
 19. The decoderaccording to claim 17, wherein the inverse quantization stage isconfigured to determine the two refined inverse quantization levels forthe zero quantized value based on the factor:fac_z=dz/3 wherein fac_z indicates a normalized absolute value by whicha normalized absolute value of the inverse quantization level is to beincreased in order to obtain a first of the two refined inversequantization levels and a normalized absolute value by which anormalized absolute value of the inverse quantization level is to bedecreased in order to obtain a second of the two refined inversequantization levels, and wherein dz is a normalized width of the deadzone.
 20. A system, comprising: an encoder according to claim 1; and adecoder according to claim
 11. 21. A method for encoding, the methodcomprising: quantizing an input signal in order to obtain a plurality ofquantized values using a dead zone; encoding the plurality of quantizedvalues using an entropy encoding scheme in order to obtain a pluralityof entropy encoded values; quantizing a residual signal caused by aquantization by the quantization stage and determining a plurality ofquantized residual values in dependence on the dead zone of thequantization stage; and forming a bit stream from the plurality ofentropy encoded values and the plurality of quantized residual values.22. A method for decoding, the method comprising: parsing a coded signalin order to obtain a plurality of entropy encoded values and a quantizedresidual value; decoding the plurality of entropy encoded values usingan entropy decoding scheme in order to obtain a plurality of quantizedvalues; inverse quantizing the plurality of quantized values in order toobtain an output signal; and refining an inverse quantization level usedfor obtaining the output signal in dependence on a dead zone and thequantized residual value.
 23. A non-transitory digital storage mediumhaving a computer program stored thereon to perform the method forencoding, the method comprising: quantizing an input signal in order toobtain a plurality of quantized values using a dead zone; encoding theplurality of quantized values using an entropy encoding scheme in orderto obtain a plurality of entropy encoded values; quantizing a residualsignal caused by a quantization by the quantization stage anddetermining a plurality of quantized residual values in dependence onthe dead zone of the quantization stage; and forming a bit stream fromthe plurality of entropy encoded values and the plurality of quantizedresidual values, when said computer program is run by a computer.
 24. Anon-transitory digital storage medium having a computer program storedthereon to perform the method for decoding, the method comprising:parsing a coded signal in order to obtain a plurality of entropy encodedvalues and a quantized residual value; decoding the plurality of entropyencoded values using an entropy decoding scheme in order to obtain aplurality of quantized values; inverse quantizing the plurality ofquantized values in order to obtain an output signal; and refining aninverse quantization level used for obtaining the output signal independence on a dead zone and the quantized residual value, when saidcomputer program is run by a computer.